A flea of negligible size is trapped in a large, spherical, inflated beach ball with radius r. At this moment, it is equally likely to be at any point within the ball. Let X be the distance of the flea from the center of the ball. Using the fact that the volume of a sphere of radius r is 4r/3, for X, find ... (a) ... the cumulative distribution function F. (b) ... the probability density function f. (c) ... the expected value. (d) ... the variance.